The invention relates to a conveyor device for transporting and expelling material to be conveyed, in particular flat items of mail, having vertically pivotable conveyor modules arranged one behind another.
By means of specific expulsion at the respective conveyor module, the material to be conveyed can be sorted into further conveyor devices or into containers associated with the conveyor modules (DE-A 2 108 023).
In order to permit short gaps between the material to be conveyed and sorted, and therefore a high throughput, it is necessary to carry out the pivoting movements even while there is still material to be conveyed on the conveyor module. For example, on a conveyor module that has already been pivoted downward into the expulsion position, there may be material to be conveyed which is actually to be transported onward horizontally. When this conveyor module is pivoted up and stops in the end position, the material to be conveyed and located loosely on the conveyor module can jump up and lose contact with the conveyor means. As a result, undefined positions of the material to be conveyed, including displacements of the gaps, may arise. Furthermore, increased wear and the high production of noise is associated with the sudden braking from the full pivoting speed.
In order to avoid the disadvantages, to configure the speed of the pivoting movement in such a way that the accelerations at the start and end of the pivoting movements are as small as possible, DE 44 38 207 A1 has already suggested the use of a crank drive with a sinusoidal movement curve to drive vertically pivotable transfer devices. In this case, after the pivoting movements for conveyance or expulsion, the conveyor module has to remain in the end positions for a certain time, in particular in the upper end position, in a stable manner. The material to be conveyed located on the respective conveyor module as the latter is pivoted up must reach the end of the conveyor module only when the latter has reached its horizontal end position, since otherwise the material to be conveyed would collide with the following conveyor module.
A further increase in the throughput by increasing the pivoting speed is not possible because of the associated danger, already outlined, of the material to be conveyed lifting off the transport plane and the gap displacements associated with this.
The invention described in claim 1 is therefore based on the object of configuring the closing operation following the expulsion in such a way that shorter distances between the materials to be conveyed are permissible without increasing the pivoting speeds.
In this case, the invention is based on the idea of shortening the closing time, during which the conveyor module part pivoted out reaches the level of the following conveyor module part again in that, in the conveying direction, the front part of the conveyor module is likewise designed such that it can be displaced in a vertical direction and, immediately after material to be conveyed has been expelled, if the next material to be conveyed is to be transported onward, this front part of the conveyor module following the conveyor module to be expelled is pivoted toward the part pivoted out for the purpose of expulsion and, when it is located with its transport level underneath the transport level of the preceding, a expelling conveyor module or at least at the same height, it is pivoted back up again. This permits the distances between the materials to be conveyed to be reduced in such a way that the next material to be conveyed and not to be expelled after the expulsion operation may reach this conveyor module before the closing movement has been completed.
Advantageous refinements of the invention are specified in the subclaims.
Thus, in order to achieve the shortest possible distances between the materials to be conveyed, it is beneficial for the front part, in the conveying direction, of the conveyor module following the expelling conveyor module, during the closing movement of the expelling conveyor module to be pivoted downward only until both conveyor modules are located with the conveyor level of their mutually adjacent parts at approximately the same height, and is then immediately pivoted upward again.
In order to reduce the outlay, it is advantageous to guide the front part, in the conveying direction, of the conveyor module vertically rectilinearly displaceably, and to guide the rear part in such a way that the necessary horizontal movement components can be executed. In an advantageous drive variant, the front part of the conveyor module is connected to a controllable lifting element. A lifting magnet or a pneumatic lifting cylinder, for example, can be employed as the lifting element.
A spring element can also act on the front part, in the conveying direction, of the conveyor module as an energy store.
In addition, to achieve a sinusoidal vertical movement curve, it is advantageous to connect the rear part, in the conveying direction, of the conveyor module to the push rod of a crank drive.